Microstructure and strengthening mechanisms of 90W–7Ni–3Fe alloys prepared using laser melting deposition

• Published in: Journal of alloys and compounds Vol. 838; p. 155545
• Main Authors: Wang, Y.P., Ma, S.Y., Yang, X.S., Zhou, Y.Z., Liu, X., Li, J.F., Zhang, J.J., Li, C., Wang, X.Y., Le, G.M., Zhang, Y.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 15.10.2020; Elsevier BV
• Subjects: Bonding strength; Composites; Cooling effects; Deposition; Dislocation density; Laser beam melting; Laser deposition; Liquid phase sintering; Liquid phases; Mechanical properties; Mechanical property; Microstructure; Refractory metals; Strengthening; Tungsten base alloys; Refractory metals; Composites; Microstructure; Mechanical property; Laser deposition
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2020.155545

The microstructure and mechanical properties of a 90W–7Ni–3Fe heavy alloy manufactured using laser melting deposition (LMD) have been investigated with a goal of understanding the LMD process and the relevant strengthening mechanisms. A reference sample prepared using liquid phase sintering (LPS) with similar composition has been used for comparison to isolate effects of the processing rate. The results show that the nearly fully-dense LMD sample consists of two periodically alternating sublayers containing different volume fractions of W particles. Compared to the reference LPS sample, the LMD sample has a higher W content in the binder matrix, a more refined microstructure, a higher dislocation density and a lower contiguity between W particles. Furthermore, the LMD sample has a yield strength of 822 ± 30 MPa, which is about 200 MPa higher than that of the reference LPS sample. This strength difference is quantitatively analyzed based on the microstructural observations. It is shown that the increased fraction of W-matrix interfaces, a higher interface bonding strength and more pronounced constraint effects, resulting from the higher processing temperature and fast cooling of LMD, provide extra strengthening. The present study provides an important basis for optimizing the LMD process for manufacture of high W content tungsten heavy alloys with improved mechanical properties. [Display omitted] •A dense 90W–7Ni–3Fe alloy has been fabricated using LMD.•The LMD alloy has unique microstructures and high strength.•Fast heating and cooling rates of LMD lead to enhanced constraint effects.